A multipoint-to-multipoint communications network typically has scalability. challenges as the number of end points and/or local area network (LAN) segments increases dramatically. For example, a VPLS (virtual private LAN service) network faces scalability challenges in two dimensions: (a) in a LDP (label distribution protocol) based signaling plane due to the requirement of a full mesh among VPLS peers; and (b) in the data forwarding plane due to the requirement that each VPLS instance be aware of all the MAC (media access control) addresses in that VPLS instance. Although (a) can be addressed using spoke connectivity as defined by hierarchical VPLS; however, even with hierarchical VPLS, each VPLS instance still needs to maintain the entire MAC table for that instance which presents significant scaling problems for a large VPLS network.
FIG. 1 is a block diagram illustrating a typical network configuration. FIG. 1 shows a single LAN that is geographically distributed across three provider edge (PE) boxes. All hosts connected to the LAN (regardless of the attachment PE) belong to the same IP network. The PE devices provide network level layer 2 bridging/VPLS services to interconnect the distributed LAN segments. Referring to FIG. 1, local nodes 108-113 are part of the same LAN—bridging across the LAN segments is provided by their attachment PE devices—PE A, PE B, and PE C respectively. Typically, in a layer 2 (e.g., MAC layer) switching configuration, each of the PE devices (A, B, and C) has to maintain a MAC table to maintain all of the MAC addresses of all nodes 108-113, in order to properly forward data from a source MAC address to a destination MAC address of any one of nodes 108-113. As the number of nodes 108-113 increases significantly, the MAC table maintained within each PE device (e.g., PE devices A, B, and C) will significantly increase leading to scalability issues. Moreover, addition of another LAN segment will impact all the PE devices in the network as they now will have to learn all the MAC addresses that belong to the newly added LAN segment.